When Atlanta United thrashed the New York Red Bulls 3-0 in the first leg of the Eastern Conference finals in November, it practically guaranteed the MLS upstarts a spot in MLS Cup in only their second season in the league. It was an incredible achievement in terms of the history of the young club, but it was also a remarkable victory in a narrow sense: Smashing the Supporters’ Shield winners to such a degree, a team that only weeks before had picked Atlanta apart without several of its main contributors, represented a significant reversal. After that first-leg win by Atlanta, much of the attention centered on the New York Red Bulls and their manager, Chris Armas, who decided to move away from his team’s usual pressing style. Instead of defending in advanced areas, Armas had his team sit deep in a semi-compact block in an attempt to force Atlanta United to break them down.

The whole episode was notable for another reason: It sparked a genuine conversation about tactical...